1. Field of the Invention
The present invention relates to an image formation apparatus provided with a process cartridge unit which comprises at least a photoconductive drum and a developer.
2. Description of the Related Art
In general, prior image formation apparatuses such as an electrostatic printer include a photoconductive drum around which a series of elements are arranged for forming a latent image on the surface of the drum, developing a toner image from the latent image, and transferring the toner image to a medium.
FIG. 7 shows a main structure of such a prior type printer. In the figure, 1 is a process cartridge, 2 is a transfer-charger, and 3 is a transfer path for a medium (sheet). The process cartridge 1 includes a photoconductive drum 4, a precharger 5, a developer 6, and a cleaner 7. The developer 6 contains toner 8 and is provided with a magnetic roller 9.
The formation of a toner image on the surface of the photoconductive drum 4, and the transfer of that image, are carried out in the following manner:
First, the photoconductive drum 4 is driven to be rotated clockwise and is uniformly charged by the precharger 5. Then, a static latent image corresponding to information is formed on the surface of the drum 4 by a latent image-forming means, such as an LED array, and is developed by the developer 6 from a toner supplied thereto by the magnetic roller 9. The latent image is transferred at point (A) by the transfer-charger 2 onto a sheet which is supplied, as indicated by an arrow, through the path 3 in synchronism with the rotation of the photoconductive drum 4. After the image-transference, the sheet is conveyed to the position (B) and the toner image is fixed thereon by a fuser 10, and finally, the sheet is discharged onto a stacker. The charge on the surface of the photoconductive drum 4 is removed by a discharger, and residual toner powder is withdrawn by the cleaner 7.
In the above-described printer, however, the design is limited in practice due to the existence of the path 3 in addition to the process cartridge 1, and thus, the printer is inevitably larger in size than is desirable, and the cost of manufacturing such a printer is high.